The execution of organic synthesis in aqueous medium without the use of harmful organic solvents has long been a major object in industry.
Heretofore, various methods of reaction in aqueous mediums containing organic solvent have been proposed, but none have been practical; one major reason being that in reactions performed in aqueous mediums, organic compounds are not soluble in water.
In order to solve such problems, the inventors of the present invention have developed Lewis acid-surfactant linked catalysts comprising scandium, tris(dodecylsulfate), scandium tris(dodecylsulfonate) or the like (Kobayashi, S., Wakabayashi, T., Tetrahedron Lett. 1998, 39, 5389; Kobayashi, S., Chem. Lett. 1991, 2187; Kobayashi, S., Nagayama, S., Busujima, T., J. Am. Chem. Soc. 1998, 120, 8287).
It has been said that by using such catalysts, organic compounds would quickly dissolve in water in a colloidal manner to allow reactions such as the aldol reaction of silyl enole ethers and aldehydes to proceed smoothly, without the use of organic solvents.
Although such substantial improvements were said to be possible, in reality, for the above catalyst, its recovery from water was not necessarily easy; hence, the difficulty in recovering and purifying the reaction products were problematic.
The invention of the present application has been achieved to solve the above-described problems, based on the knowledge on Lewis acid catalysts that enable organic synthesis in aqueous medium, proposed by the inventors, to provide a novel Lewis acid catalyst, which show high reaction activity in aqueous medium, may easily be recovered and is excellent in reusability.